Leonardite is a soft waxy, black or brown, shiny, vitreous

mineraloid A mineraloid is a naturally occurring substance that resembles a mineral, but does not demonstrate the crystallinity of a mineral. Mineraloid substances possess chemical compositions that vary beyond the generally accepted ranges for specific mi ...

that is easily soluble in alkaline solutions. It is an

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

product of

lignite Lignite (derived from Latin ''lignum'' meaning 'wood'), often referred to as brown coal, is a soft, brown, combustible sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35% and is considered the lowest ...

, associated with near-surface

mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...

. It is a rich source of

humic acid Humic substances (HS) are colored relatively recalcitrant organic compounds naturally formed during long-term decomposition and transformation of biomass residues. The color of humic substances varies from bright yellow to light or dark brown lead ...

(up to 90%) and is used as a

soil conditioner A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often ...

, as a stabilizer for ion-exchange resins in water treatment, in the remediation of

polluted Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

environments and as a

drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross section (geometry), cross-section in solid materials. The drill bit is usually a rotary Cutting tool (machining), cutting tool, often multi-point. The bit i ...

additive.Hoffman, G.L., Nikols, D.J., Stuhec, S., Wilson, R.A. Evaluation of Leonardite (Humalite) Open File Report 1993-18, Resources of Alberta, Alberta Geological Survey
It was named after A. G. Leonard, first director of the North Dakota Geological Survey, in recognition of his work on these deposits.Odzoba, D.M., Blyth, J.C., Engler, R.F., Dinel, H. & Schnitzer, M. 2001. Leonardite and humified organic matter. In Ghabbour, E.A. & Davies, G. (eds.) Humic Substances: Structures, Models and Functions (Special Publication), Royal Society of Chemistry 388pp.

Formation

Leonardite is found associated with near surface lignite deposits. They are thought to have been formed by the oxidation of the lignite, an interpretation supported by chemical analysis of leonardite compared to lignite.Youngs, R.W. & Frost, C.M. 1963. Humic acids from leonardite – a soil conditioner and organic fertilizer. Ind. Eng. Chem., 55, 95–99
/ref>

Occurrence

Leonardite was first described from North Dakota and is found associated with virtually all the lignite deposits in the state. Leonardite has also been described worldwide from deposits of lignite or sub-bituminous coals e.g. in

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, in Achlada and Zeli,

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

, in

Turkey Turkey, officially the Republic of Türkiye, is a country mainly located in Anatolia in West Asia, with a relatively small part called East Thrace in Southeast Europe. It borders the Black Sea to the north; Georgia (country), Georgia, Armen ...

and in

Bacchus Marsh Bacchus Marsh ( Wathawurrung: ''Pullerbopulloke'') is a town in Victoria, Australia, located approximately north-west of the state capital Melbourne, at a near equidistance to the major cities of Melbourne, Ballarat and Geelong. As of the ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

Uses

Soil conditioner

It is used to condition soils either by applying it directly to the land, or by providing a source of humic acid or potassium humate for application. The carbon geosequestration potential of Leonardite, particularly to rapidly accelerate microbial action to lock up and retain carbon in soils, provides the basis for extensive research in

Victoria Victoria most commonly refers to: * Queen Victoria (1819–1901), Queen of the United Kingdom and Empress of India * Victoria (state), a state of Australia * Victoria, British Columbia, Canada, a provincial capital * Victoria, Seychelles, the capi ...

on the organic fertilising aspect of brown coal.

Remediation of polluted soils

Leonardite can be added directly to soils to reduce the uptake of metals by plants in contaminated ground, particularly when combined with

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by Decomposition, decomposing plant and food waste, recycling organic materials, and man ...

Drilling additive

Leonardite is used to stabilise and thin the

drilling fluid In geotechnical engineering, drilling fluid, also known as drilling mud, is used to aid the drilling of boreholes into the earth. Used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also use ...

used to make in oil, gas, and

geothermal Geothermal is related to energy and may refer to: * Geothermal energy, useful energy generated and stored in the Earth * Geothermal activity, the range of natural phenomena at or near the surface, associated with release of the Earth's internal he ...

wells. It was first employed extensively during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

when

quebracho tannin Quebracho is a common name in Spanish language, Spanish to describe very hard (density 0.9–1.3) wood tree species. The etymology of the name derived from ''quiebrahacha'', or ''quebrar hacha'', meaning "axe-breaker". The corresponding English- ...

became difficult to obtain.Darley, H.C.H. & Gray, D.R. 1988. Composition and properties of drilling and completion fluids, Gulf Professional Publishing, 644pp.
/ref> It has very good temperature stability and prevents solidification of lime muds near 150 °C.

References

External links

{{Commons category
Victoria Australia Brown Coal Factsheet
Coal Organic minerals Soil improvers